Effects of quenching temperature on microstructure and mechanical properties of H13 mandrel steel

Optical microscope, stereomicroscope, scanning electronic microscope （SEM） and mechanical property testing were used to research the effects of different quenching temperatures on the microstructure and mechanical properties of the H13 mandrel steel. The results indicate that following an increase in the quenching ,the degree of alloying is enhanced due to the carbides dissolving gradually in austenite, which improves the hardenability of the specimens, as well as their room and high-temperature strength. At the same time, the fracture toughness increases due to the increment of the martensite number and the interparticle distance of impact toughness. Optimal performance Consequently,the service life of the H13 the carbides. However, extremely coarse grain and martensite can decrease the can be obtained after quenching at 1 060℃ and double tempering at 620℃mandrel steel is extended significantly.

Study of the influence of heat treatment procedure on the microstructure and mechanical properties of H13 mandrel steel

In this study,the microstructural evolution of H13 mandrel steel during its manufacturing process and the influence of the preheat treatment procedure and the second-step tempering temperature on its microstructural and mechanical properties were investigated.The experiment results showed that,using an H13 mandrel steel billet in the as-annealed condition produced by Baosteel as a raw material,the preheat treatments of normalization,spheroidization annealing,or normalization plus spheroidization annealing,as described in this paper,had no significant effect on the final mechanical properties after quenching and tempering.H13 mandrel steel met all the mechanical property requirements via quenching and tempering without preheat treatment.In the temperature range from 600 to 680 t,with an increase in the second-step tempering temperature,the strength gradually decreased whereas the plasticity and toughness gradually improved.Using the quenching-plus-first-tempering procedure of 1030℃/l h/oil cooling+600℃/5 h/air cooling,good balance between strength and toughness could be achieved by selecting 650℃ as the second-step tempering temperature.The test results also showed that the holding time of the second tempering played a big role in the mechanical properties.When this holding time was extended from 1 to 2 h,the hardness of the H13 mandrel steel decreased and the extent of this reduction increased with an increase in the second-step tempering temperature.In the temperature range of 1030 to 1090℃,the yield strength,tensile strength,and hardness gradually increased,however,the impact toughness decreased with increases in the quenching temperature.

Effects of the refining treatment on the microstructure and the mechanical properties of H13 mandrel

This study researches the effects of the refining treatment on the microstructure and the mechanical properties of H13 mandrel steel and compares these effects with those of the conventional treatment. The results indicate that both carbide particles and grains were refined, carbide particles were uniformly distributed by the refining treatment, and therefore,the strength and toughness of H13 mandrel steel were improved. Rapid cooling after the solution treatment may inhibit intra-granular precipitation of carbide particles, which is favorable to enhancing toughness. Consequently, high- performance H13 mandrel steel can be produced by proper refining treatment.

影响H13芯棒钢冲击韧性的因素分析

由于H13芯棒本身的特性及其特殊使用条件,冲击韧性是影响其使用寿命的主要因素。通过显微组织观察,分析了某厂所产H13芯棒钢冲击韧性低的原因。研究结果表明:枝晶偏析、带状偏析、液析碳化物及存在于晶界或马氏体边界的二次碳化物,是导致芯棒冲击韧性降低的主要原因。通过制定合理的电渣工艺,并采用高温扩散退火和大锻造比反复多向锻造,锻后及热处理后采用快冷,可避免上述问题的发生,从而达到提高芯棒冲击韧性的目的。

H13钢轧机芯棒的热处理工艺研究

通过对国产芯棒材料的热处理试验,获取了大量实验数据。经过筛选和优化,获得了H13钢轧机芯棒的热处理生产工艺,为实现计算机辅助热处理工艺设计(CAPP)提供基础数据,同时也对H13钢的应用进行深入探讨。

热处理工艺对H13芯棒钢组织和力学性能的影响

研究了H13芯棒钢在制造工艺过程中的组织演变规律和预备热处理工艺、二次回火温度对其组织和力学性能的影响。研究结果表明,采用宝钢出厂退火态的H13芯棒坯材料,调质前采用文中的正火或球化或正火+球化三种工艺进行预备热处理对最终调质后的力学性能无显著影响,直接调质的H13芯棒钢的各项力学性能指标可以满足设计要求;在600~680℃范围内,随着二次回火温度的升高,材料强度逐渐下降,但塑性、韧性逐渐改善。在1 030℃/保温1 h/油淬+600℃/保温5 h/空冷的淬火+一次回火的工艺条件下,二次回火温度选择650℃可以获得良好的强韧性匹配;二次回火保温时间对性能也有显著影响,二次回火保温时间从1 h增加至2 h,H13芯棒钢的硬度值降低,且随着二次回火温度的升高,该降低幅度逐渐增大;在1 030~1 090℃,随着淬火加热温度的升高,H13芯棒钢的屈服强度、抗拉强度和硬度逐渐增加,但冲击韧性有所降低。

H13钢芯棒冲击韧性偏低的原因分析

H13钢作为钢管轧制用芯棒,对其冲击韧性有一定要求。生产中发现某电渣重熔H13钢芯棒冲击韧性偏低。本文通过光学显微镜以及扫描电镜等手段分析了钢中块状共晶碳化物以及非金属夹杂物。结果表明,冲击韧性低的主要原因是钢中存在带状组织、大块的共晶碳化物以及非金属夹杂物。非金属夹杂物中发现了带有棱角的（Ti,V）CN型氮化物、圆形的Al_2O_3和Ca O·Al_2O_3,以及包覆着Al_2O_3和Mg O·Al_2O_3核心的方形氮化物。

钢管卧式挤压机用H13挤压针早期失效原因分析

从裂纹形貌、硬度、残余奥氏体、显微组织、使用等方面对挤压生产不锈钢钢管用H13挤压针开裂甚至断裂的早期失效原因进行了分析。结果表明:在挤压钢管过程中,H13挤压针冷却不良,使挤压针表面发生二次淬火是挤压针开裂的主要原因。提出了通过改造挤压针的冷却系统、热处理工艺等措施,可提高其使用寿命。

连轧管机用4Cr5MoSiV1限动芯棒材料的研制

连轧管机组限动芯棒工作环境极为恶劣,需要经受激冷激热的热循环应力和循环交变机械应力同时作用,对芯棒材料的韧性和耐热疲劳性要求非常高。通过系统分析4Cr5MoSiV1(H13)钢连轧管机组限动芯棒的工作环境、应力状态,确定了限动芯棒的关键力学性能是高温蠕变强度、横向冲击韧性和耐热疲劳性。采用EBT+LF+VD精炼、初轧机轧制电极棒、双极串联电渣重熔、锻造开坯、轧制成材的工艺路线进行了芯棒退火毛坯的试制;经过能力试样性能检验合格后,采用组织预先处理、粗车、淬回火热处理、精车、镀铬的工艺流程,成功研制出规格为(Φ166.4～Φ181.2)×11 500 mm的4Cr5MoSiV1(H13)钢连轧管机限动芯棒成品。对实际限动芯棒成品取样进行化学成分、非金属夹杂物、晶粒度、拉伸、冲击等力学性能,以及芯棒表面硬度均匀性、超声波探伤、芯棒尺寸精度和弯曲度等项目的检验,结果均符合连轧管机限动芯棒技术条件的要求。本研究实现了限动芯棒国产化,"以产顶进"的经济效益和社会效益显著。

高温均匀化退火对H13钢芯棒带状偏析和冲击性能的影响

采用热轧态H13钢芯棒进行高温均匀化退火试验,研究了不同的保温温度、时间及冷速对带状偏析和冲击性能的影响。结果表明,H13钢在1250℃均匀化退火4 h,经快速冷却后,带状偏析明显减轻,二次碳化物和杂质元素在晶界偏聚倾向减小,冲击性能及等向性均得到提高。经生产实践检验,钢锭在锻造前进行1250℃均匀化处理,锻后快冷,钢材性能基本达到进口8407钢水平。